Postoperative atrial fibrillation (poAF) following cardiac surgery has been associated with increased rates of mortality, hospital readmissions, and other complications. Despite efforts to prevent this complication, the frequency of poAF remains high—approximately 30% for coronary artery bypass grafting and as high as 50% for combined coronary valve operations. Although many cardiac surgeons have come to regard poAF as nothing more than a nuisance, numerous studies have linked this complication with higher short- and long-term mortality and other major complications, such as bleeding and stroke. Inevitably, poAF results in higher costs and worse outcomes for patient care. Even more frustrating than inadequate prevention strategies is the lack of proven treatment strategies for patients who develop poAF. Gillinov et al. [1Gillinov A.M. Bagiella A.J. Moskowitz J.M. et al.Rate control versus rhythm control for atrial fibrillation after cardiac surgery.N Engl J Med. 2016; 374: 1911-1921Crossref PubMed Scopus (213) Google Scholar] failed to show an advantage for either a rhythm control or rate control strategy for patients who developed poAF. Furthermore, 25% of patients in each group deviated from their assigned therapy because of drug ineffectiveness. Also lacking are well-defined, adopted guidelines and protocols regarding when anticoagulation should be initiated and for how long. As cardiac surgeons, we have all experienced the consequences of poAF in our patients, namely prolonged hospitalization, readmissions, and complications from poorly controlled anticoagulation regimens. In this issue of The Annals, Sigurdsson and colleagues [2Sigurdsson M.I. Longford N.T. Heydarpour M. et al.Duration of postoperative atrial fibrillation after cardiac surgery is associated with worsened long-term survival.Ann Thorac Surg. 2016; 102: 2018-2027Abstract Full Text Full Text PDF PubMed Scopus (17) Google Scholar] are to be congratulated on their efforts to quantify the negative effects of poAF on long-term survival in cardiac surgery patients. Their data add to the growing body of evidence that poAF is associated with deleterious consequences. The authors’ use of propensity score matching, and the Elixhauser comorbidities index allowed for a rigorous statistical comparison between groups. The prospective nature of the study, albeit observational, also increases the validity of the results. Not unlike other large observational studies, this analysis raises more questions than it answers. The choice of 2 days as the cutoff for the definition of prolonged AF is somewhat arbitrary. What this really means to readers is that patients who fail to have their AF corrected, regardless of treatment choice, are more likely to have worse long-term survival. In the CTS Network trial by Gillinov et al. [1Gillinov A.M. Bagiella A.J. Moskowitz J.M. et al.Rate control versus rhythm control for atrial fibrillation after cardiac surgery.N Engl J Med. 2016; 374: 1911-1921Crossref PubMed Scopus (213) Google Scholar], greater than 90% of patients, regardless of a rhythm or rate control strategy, had resolution of AF by 60 days. The results in this current issue are complementary. What is still not clearly defined is whether poAF is simply associated with worse long-term outcomes or there is truly causation. Despite rigorous statistical methods such as the comorbidity index described above or propensity score matching, it is difficult to control for variables that are unknown or unmeasured. Even in this study, the authors suggest that confounding might have a role in the results. Patients with prolonged poAF were older and had more comorbidities, longer bypass times, and a higher incidence of concomitant coronary and valve surgery. Was it the poAF that was responsible for the increased mortality? Until we have these answers, it would be prudent to heed the results of a growing body of evidence suggesting that poAF is strongly associated with worse survival in patients undergoing cardiac surgery. Duration of Postoperative Atrial Fibrillation After Cardiac Surgery Is Associated With Worsened Long-Term SurvivalThe Annals of Thoracic SurgeryVol. 102Issue 6PreviewStudies of the effects of postoperative atrial fibrillation (poAF) on long-term survival are conflicting, likely because of comorbidities that occur with poAF and the patient populations studied. Furthermore, the effects of poAF duration on long-term survival are poorly understood. Full-Text PDF